Methods and apparatus for utilizing short transmission time intervals in a wireless communications network

ABSTRACT

The disclosure provides a method in a terminal device for a wireless communication network. The terminal device is configurable with a plurality of transmission time intervals. The method comprises; receiving a first grant message from the wireless communication network, the first grant message comprising an indication of first radio resources in which the terminal device can transmit one or more wireless messages, the first radio resources being configured according to a first transmission time interval of the plurality of transmission time intervals; determining the presence of data to transmit, the data being associated with a first logical channel; determining a maximum transmission time interval associated with the first logical channel; and, responsive to a determination that the maximum transmission time interval associated with the logical channel is less than the first transmission time interval, transmitting a scheduling request message to the wireless communication network. The scheduling request message is configured according to a second transmission time interval of the plurality of transmission time intervals, which is shorter than the first transmission time interval.

TECHNICAL FIELD

Embodiments of the present disclosure relate to methods and apparatus ina wireless communication network, and particularly to methods andapparatus for enabling low-latency communications between two wirelessdevices, or between a wireless device and the wireless communicationnetwork.

BACKGROUND

Efforts are on-going to develop and standardize communications networksand protocols intended to meet the requirements set out for the fifthgeneration (5G) of wireless systems, as defined by the Next GenerationMobile Networks Alliance. Such networks are expected to support a largenumber of use cases, with different use cases having widely differentrequirements in terms of the service provided by the network.

For example, some use cases may require that data be transmitted andreceived with extremely low latency, whereas other use cases may havemore relaxed latency requirements. In the former category, it isenvisaged that future networks may allow for the remote control ofmachinery, or surgical instruments. In such cases, it is important thatdata transmitted between the controller (e.g. a surgeon) and thecontrolled device (e.g., surgical instruments) is reliable and has lowlatency. A class of communications requiring such performance has beendefined as “ultra-reliable and low-latency communications” (URLLC). See,“Study on New Radio Access Technology; Radio Interface Protocol Aspects”(3GPP TR 38.804, v0.4.0). Note that URLLC traffic is applicable in awide range of use cases not limited to the surgical/machinery examplesset out above. Other communications requiring low latency may becritical machine-type communications (C-MTC). Conversely, in the lattercategory, large-scale sensor networks and other reporting mechanisms forwireless devices may have no need for low latency. For example, massivemachine-type communications (M-MTC) may fall within this category.

Thus, in the present Long Term Evolution (LTE) system and also in futuresystems, there are many different types of services with differentcorresponding quality of service (QoS). Such services are typicallymapped to corresponding logical channels and each logical channel isassociated with a preconfigured logical channel priority (LCP).According to the LCP values, a scheduler in the radio access network(RAN) can flexibly allocate the resources to different logical channelsin accordance with the LCP values (e.g., allocating resources to logicalchannels with higher priority before allocating resources to logicalchannels with lower priority). In this way, high-latency services may bemultiplexed with other less latency-dependent services.

Current versions of LTE are based on a repeated frame structure in whicha frame comprises 10 subframes, each of 1 ms length and consisting of 14orthogonal frequency-division multiplexed (OFDM) symbols. In downlink(DL), the first four symbols or fewer in each subframe comprise acontrol channel (i.e. the physical downlink control channel, PDCCH),while the remaining symbols comprise a data channel (i.e. the physicaldownlink shared channel, PDSCH). In uplink (UL), all symbols can be usedfor the transmission of data (i.e. via the physical uplink sharedchannel, PUSCH), while some symbols may be used for control information(i.e. via the physical uplink control channel, PUCCH) and referencesymbols.

In LTE, scheduling and transmission are defined on the timescale ofsubframes. That is, terminal devices are scheduled to transmit orreceive messages using radio resources that are defined in terms ofwhole subframes. This timescale is often referred to as the transmissiontime interval (TTI), i.e. the duration of a transmission on the radiolink. Thus the standard TTI in LTE is one subframe, or 14 OFDM symbols.

The current solutions for achieving low latency in LTE rely on the LCPvalues associated with logical channels. However, transmissions arestill limited to TTIs which are 14 symbols long.

A method of reducing this latency still further is desirable,particularly for classes of data requiring extremely low latency.

SUMMARY

Apparatus and methods are disclosed that alleviate some or all of theproblems discussed above.

Currently, work in 3GPP is ongoing to standardize “short TTI” or “sTTI”operation, where scheduling and transmission can be done on a fastertimescale. One way of achieving this is to subdivide the legacy LTEsubframe into several sTTI. The supported lengths currently beingdiscussed for sTTI are 2 and 7 OFDM symbols. However, other lengths maybe defined in future and the present disclosure is not limited to anyparticular values of TTI. Data transmission in DL may happen per sTTIvia the short PDSCH (or sPDSCH), which may include a control regioncorresponding to the short PDCCH (or sPDCCH). In UL, data is transmittedper sTTI via the short PUSCH (sPUSCH); control information can betransmitted via the short PUCCH (sPUCCH).

With the introduction of short TTI, which can be scheduled dynamicallywithin regular TTI of 1 ms, data may be transmitted with high or lowlatency. For overall data delivery, beside the frame duration, alsorelated processing times are important to consider for the overalldelivery time.

One aspect of the present disclosure provides a method in a terminaldevice for a wireless communication network, the terminal device beingconfigurable with a plurality of transmission time intervals. The methodcomprises: receiving a first grant message from the wirelesscommunication network, the first grant message comprising an indicationof first radio resources in which the terminal device can transmit oneor more wireless messages, the first radio resources being configuredaccording to a first transmission time interval of the plurality oftransmission time intervals; determining the presence of data totransmit, the data being associated with a first logical channel;determining a maximum transmission time interval associated with thefirst logical channel; and, responsive to a determination that themaximum transmission time interval associated with the logical channelis less than the first transmission time interval, transmitting ascheduling request message to the wireless communication network, thescheduling request message being configured according to a secondtransmission time interval of the plurality of transmission timeintervals, wherein the second transmission time interval is shorter thanthe first transmission time interval.

Another aspect provides a terminal device for a wireless communicationnetwork, the terminal device being configurable with a plurality oftransmission time intervals. The terminal device is configured to:receive a first grant message from the wireless communication network,the first grant message comprising an indication of first radioresources in which the terminal device can transmit one or more wirelessmessages, the first radio resources being configured according to afirst transmission time interval of the plurality of transmission timeintervals; determine the presence of data to transmit, the data beingassociated with a first logical channel; determine a maximumtransmission time interval associated with the first logical channel;and, responsive to a determination that the maximum transmission timeinterval associated with the logical channel is less than the firsttransmission time interval, transmit a scheduling request message to thewireless communication network, the scheduling request message beingconfigured according to a second transmission time interval of theplurality of transmission time intervals, wherein the secondtransmission time interval is shorter than the first transmission timeinterval.

A further aspect provides a terminal device for a wireless communicationnetwork, the terminal device being configurable with a plurality oftransmission time intervals and comprising processing circuitry and anon-transitory computer-readable medium storing instructions which, whenexecuted by the processing circuitry, cause the terminal device to;receive a first grant message from the wireless communication network,the first grant message comprising an indication of first radioresources in which the terminal device can transmit one or more wirelessmessages, the first radio resources being configured according to afirst transmission time interval of the plurality of transmission timeintervals; determine the presence of data to transmit, the data beingassociated with a first logical channel; determine a maximumtransmission time interval associated with the first logical channel;and, responsive to a determination that the maximum transmission timeinterval associated with the logical channel is less than the firsttransmission time interval, transmit a scheduling request message to thewireless communication network, the scheduling request message beingconfigured according to a second transmission time interval of theplurality of transmission time intervals, wherein the secondtransmission time interval is shorter than the first transmission timeinterval.

Another aspect provides a terminal device for a wireless communicationnetwork, the terminal device being configurable with a plurality oftransmission time intervals and comprising: a first module configured toreceive a first grant message from the wireless communication network,the first grant message comprising an indication of first radioresources in which the terminal device can transmit one or more wirelessmessages, the first radio resources being configured according to afirst transmission time interval of the plurality of transmission timeintervals; a second module configured to determine the presence of datato transmit, the data being associated with a first logical channel; athird module configured to determine a maximum transmission timeinterval associated with the first logical channel; and a fourth moduleconfigured to, responsive to a determination that the maximumtransmission time interval associated with the logical channel is lessthan the first transmission time interval, transmit a scheduling requestmessage to the wireless communication network, the scheduling requestmessage being configured according to a second transmission timeinterval of the plurality of transmission time intervals, wherein thesecond transmission time interval is shorter than the first transmissiontime interval.

Note that the discussion below focuses on a technical solution for LTEand the developments thereto that are intended to meet the criteria for5G networks; however, those skilled in the art will appreciate that itis also possible to apply the methods and apparatus described herein toother networks and access technologies.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communications network;

FIG. 2 shows a processing flow according to embodiments of thedisclosure;

FIG. 3 is a flow chart of a method according to embodiments of thedisclosure;

FIG. 4 is a schematic diagram of a wireless terminal device according toembodiments of the disclosure; and

FIG. 5 is a schematic diagram of a wireless terminal device according tofurther embodiments of the disclosure.

DETAILED DESCRIPTION

The following sets forth specific details, such as particularembodiments for purposes of explanation and not limitation. But it willbe appreciated by one skilled in the art that other embodiments may beemployed apart from these specific details. In some instances, detaileddescriptions of well-known methods, nodes, interfaces, circuits, anddevices are omitted so as not obscure the description with unnecessarydetail. Those skilled in the ark will appreciate that the functionsdescribed may be implemented in one or more nodes using hardwarecircuitry (e.g., analog and/or discrete logic gates interconnected toperform a specialized function, ASICs, PLAs, etc.) and/or using softwareprograms and data in conjunction with one or more digitalmicroprocessors or general purpose computers that are specially adaptedto carry out the processing disclosed herein, based on the execution ofsuch programs. Nodes that communicate using the air interface also havesuitable radio communications circuitry. Moreover, the technology canadditionally be considered to be embodied entirely within any form ofcomputer-readable memory, such as solid-state memory, magnetic disk, oroptical disk containing an appropriate set of computer instructions thatwould cause a processor to carry out the techniques described herein.

Hardware implementation may include or encompass, without limitation,digital signal processor (DSP) hardware, a reduced instruction setprocessor, hardware (e.g., digital or analog) circuitry including butnot limited to application specific integrated circuit(s) (ASIC) and/orfield programmable gate array(s) (FPGA(s)), and (where appropriate)state machines capable of performing such functions.

In terms of computer implementation, a computer is generally understoodto comprise one or more processors, one or more processing modules orone or more controllers, and the terms computer, processor, processingmodule and controller may be employed interchangeably. When provided bya computer, processor, or controller, the functions may be provided by asingle dedicated computer or processor or controller, by a single sharedcomputer or processor or controller, or by a plurality of individualcomputers or processors or controllers, some of which may be shared ordistributed. Moreover, the term “processor” or “controller” also refersto other hardware capable of performing such functions and/or executingsoftware, such as the example hardware recited above.

Although the description is given for a wireless terminal device, oruser equipment (UE), it should be understood by the skilled in the artthat “UE” is a non-limiting term comprising any mobile or wirelessdevice, terminal or node equipped with a radio interface allowing for atleast one of: transmitting signals in uplink (UL) and receiving and/ormeasuring signals in downlink (DL). A UE herein may comprise a UE (inits general sense) capable of operating or at least performingmeasurements in one or more frequencies, carrier frequencies, componentcarriers or frequency bands. It may be a “UE” operating in single- ormulti-radio access technology (RAT) or multi-standard mode. As well as“UE”, the terms “mobile station” (“MS”), “mobile device” and “terminaldevice” may be used interchangeably in the following description, and itwill be appreciated that such a device does not necessarily have to be‘mobile’ in the sense that it is carried by a user. Instead, the term“mobile device” encompasses any device that is capable of communicatingwith communication networks that operate according to one or more mobilecommunication standards, such as the Global System for Mobilecommunications, GSM, UMTS, Long-Term Evolution, LTE, IEEE 802.11 or802.16, etc.

The description involves communication between a UE and a radio accessnetwork, which typically includes multiple radio access nodes. In thespecific example given, the radio access nodes take the form of eNodeBs(eNBs), as defined by 3GPP, or gNodeBs (gNBs) as utilised in the futurestandards expected to meet the 5G requirements. However, it will beappreciated that the concepts described herein may involve any radioaccess nodes. Moreover, where the following description refers to stepstaken in or by a radio access node, this also includes the possibilitythat some or all of the processing and/or decision making steps may beperformed in a device that is physically separate from the radio antennaof the radio access node, but is logically connected thereto. Thus,where processing and/or decision making is carried out “in the cloud”,the relevant processing device is considered to be part of the radioaccess node for these purposes.

FIG. 1 shows a network 10 that may be utilized to explain the principlesof embodiments of the present disclosure. The network 10 comprises firstand second radio access nodes 12, 14 which are connected, via a backhaulnetwork 20, to a core network 18.

The radio access nodes 12, 14 may be referred to as e.g. base stations,NodeBs, evolved NodeBs (eNB, or eNodeB), gNodeBs, base transceiverstations, Access Point Base Stations, base station routers, Radio BaseStations (RBSs), macro base stations, micro base stations, pico basestations, femto base stations, Home eNodeBs, relays and/or repeaters,beacon devices or any other network node configured for communicationwith wireless devices over a wireless interface, depending e.g. on theradio access technology and terminology used.

A wireless terminal 16 (also referred to as a wireless device, or UE) isin wireless communication with the radio access node 12. For example,the wireless terminal 16 may be camped on a cell which the radio accessnode 12 serves. Messages transmitted by the wireless terminal 16 to theradio access node 12 are said to be transmitted in the “uplink”, whilemessages transmitted by the radio access node 12 to the wirelessterminal 16 are said to be transmitted in the “downlink”.

Although not explicitly shown in FIG. 1, the wireless terminal 16 mayalso be able to communicate wirelessly with the second radio access node14. For example, the wireless terminal 16 may be configured with dualconnectivity, whereby one or more radio bearers are established betweenthe terminal 16 and each of the first and second radio access nodes 12,14, or whereby one or more radio bearers are split between the first andsecond radio access nodes 12, 14 (or a combination of both).

Also shown in FIG. 1 is a second wireless terminal 22. The secondwireless terminal 22 may be in communication with a radio access node(whether one or both of the radio access nodes 12, 14, or another radioaccess node not illustrated). However, for present purposes it can beseen that the second wireless terminal 22 is in direct communicationwith the first wireless terminal 16. Thus the first wireless terminal 16may also be capable of establishing a direct device-to-device (D2D)communication link with a second wireless terminal 22. Messagestransmitted over such a link may be referred to as “sidelink” messages.

In general terms, uplink communications take place as follows. Data istransmitted on the uplink using grants of radio resources from the radioaccess network (i.e. from a serving radio access node). Upon determiningthe presence of uplink data in its buffers to be transmitted, a wirelessterminal transmits a buffer status report to the radio access node usinguplink radio resources previously granted to the wireless terminal. Thebuffer status report contains an indication of the amount of uplink datato be transmitted. If no uplink radio resources in which to transmit thebuffer status report are granted to the terminal, the terminal may firsttransmit a scheduling request to the radio access node, requesting thegrant of radio resources in which to transmit the buffer status report.The radio access node receives and decodes the buffer status report, andschedules resources (e.g. frequencies, time slots and/or orthogonalcodes) for the wireless terminal in which to transmit the data in theuplink. The scheduled resources (i.e., an UL grant) are indicated to thewireless terminal in a downlink control message. The wireless terminalcan then subsequently utilize the granted resources for the transmissionof the data to the radio access network.

As noted above, sidelink communications are direct device-to-devicecommunications between two or more wireless terminals. Sidelink datacommunications are transmitted using resources selected from a resourcepool that is reserved for sidelink transmissions. There are currentlytwo modes of selecting the resources: in transmission mode 1, a servingradio access node selects resources for the transmitting wirelessterminal, and communicates those resources via a downlink controlmessage; in transmission mode 2, the transmitting wireless terminalself-selects the resources, e.g. according to rules aimed at minimizinginterference. Thus in transmission mode 1, a radio access node mayschedule resources for the transmitting wireless terminal to transmitdata to a receiving wireless terminal.

It will also be understood by those skilled in the art that radioresources are defined utilizing one or more of: frequencies, time slots,and orthogonal codes. The time over which a wireless terminal isscheduled to transmit or receive a communication (i.e. the time overwhich a transmission takes place) is known as the transmission timeinterval (TTI). In current versions of LTE, the TTI is 1 ms (i.e. onesubframe) and corresponds to 14 OFDM symbols; however, developments ofthe LTE standards have introduced new, shorter TTIs of 2 and 7 OFDMsymbols. Thus a wireless communications network according to embodimentsof the disclosure is operable to configure transmissions (whetheruplink, downlink or sidelink) utilizing a plurality of different TTIs;however, the disclosure is not limited to LTE, or the particular valuesof 2, 7 and 14 OFDM symbols. Rather, any plurality of different TTIvalues is contemplated.

It is further understood that data to be transmitted by a wirelessterminal (whether in the uplink or the sidelink) may be arranged inaccordance with one or more logical channels. That is, each data packetto be transmitted may belong to a particular logical channel. Logicalchannels may be associated with respective qualities of service suchthat, in general, a first logical channel may require a differentquality of service to a second logical channel. The differing quality ofservice may be implemented by means of respective logical channelpriority (LCP) values associated with each logical channel. Data for alogical channel associated with a first, relatively high LCP value maybe scheduled for transmission before data for a logical channelassociated with a second, relatively low LCP value. That is, datapackets may be assigned for transmission in the wireless terminal usingavailable granted resources (whether uplink or sidelink); data packetsfor a logical channel having the first LCP value are assigned to theavailable resources before data packets for a logical channel having thesecond LCP value. If the granted resources are sufficient, the datapackets for both logical channels may nonetheless be transmitted usingthe same radio resources.

According to embodiments of the disclosure, logical channels may furtherbe associated with a maximum TTI value. That is, each logical channelmay be associated with a respective maximum TTI value, such that datafor each logical channel is transmitted using radio resources that aredefined in accordance with a TTI value that is less than or equal to themaximum TTI value associated with the logical channel. Put another way,data for a particular logical channel is not transmitted using resourcesdefined by reference to a TTI that is greater than the maximum TTIassociated with the particular logical channel.

Thus logical channels with particularly low latency requirements may beassociated with a relatively low maximum TTI value, whereas logicalchannels with more-relaxed latency requirements may be associated with arelatively high maximum TTI value.

The maximum TTI values, as well as the LCP values and other parametersassociated with each logical channel, may be configured via signallingbetween the radio access network and the wireless terminal, e.g. usingradio resource control (RRC) signalling. The configuration of parametersmay be static or semi-static. For example, the parameters for aparticular logical channel may persist until further notice, or requireupdating from the radio access network. The parameters may be updatedperiodically, or on an ad-hoc basis.

FIG. 2 shows a processing flow according to embodiments of thedisclosure, for the example of transmission over the uplink. The processis equally applicable to sidelink transmissions, however.

The upper part of FIG. 2 shows uplink radio resources that are grantedto a particular wireless terminal. Note that the figure shows only thegrant of radio resources in the time domain, i.e. horizontally along thepage. Frequencies or codes to be used within those granted time slotsare not illustrated (and may be consistent or change from time slot totime slot). The lower part of the figure shows data in the UL buffers ofthe wireless terminal, i.e. data in the buffers of the terminal that isto be transmitted in the uplink.

It can be seen that a first period 50 of radio resources granted to thewireless terminal has a relatively long TTI, e.g. 14 OFDM symbols.However, within the period 50, one or more transmission opportunitiesare defined having shorter TTI than the overall period. Thesetransmission opportunities correspond to control transmissionopportunities for the wireless terminal to transmit control informationto the radio access node using a shorter TTI. For example, theopportunities may correspond to short PUCCH opportunities.

In the illustrated embodiment, six short transmission opportunities areshown in the long TTI 50; however, in general, any number of shorttransmission opportunities may be provided for in the long TTI 50.

At the end of the time period 50, and the beginning of a subsequentperiod 52, the wireless terminal determines the presence of data in itsUL data buffers. The data comprises data for a first logical channel LC1and a second logical channel LC2, associated with respective logicalchannel priority values. In this example, logical channel LC2 isassociated with a higher priority value than logical channel LC1

The logical channels are further associated with respective maximum TTIvalues. In the illustrated example, the first logical channel isassociated with a first maximum TTI value, e.g. 14 OFDM symbols orlonger, whereas the second logical channel is associated with a shortermaximum TTI value, e.g. 2 OFDM symbols. In this way, the data associatedwith the second logical channel may be identified as requiring lowerlatency than the data associated with the first logical channel.

At this point in time, the wireless terminal is granted only radioresources associated with a relatively long TTI, e.g. 14 OFDM symbols.According to embodiments of the disclosure, upon determining that themaximum TTI of the second logical channel is shorter than the TTIassociated with available granted resources (or upon determining that noresources have been granted), the wireless terminal transmits a controlmessage requesting the grant of resources associated with a TTI that isequal to or shorter than the maximum TTI value associated with thesecond logical channel. For example, the control message may comprise ascheduling request message transmitted over an uplink control channel.The control message may be transmitted using one or more of the shorttransmission opportunities defined within the longer TTI, and thus, inone example, the control message is transmitted as a scheduling requestover the sPUCCH.

In the illustrated embodiment, the control message is transmitted usingthe first-available short transmission opportunity upon detection, andsuch embodiments serve to keep latency for the second logical channellow. However, in other embodiments it may not be possible to transmitthe control message immediately upon detection of the data in thebuffers, and thus a short delay is possible until a subsequenttransmission opportunity.

The first logical channel is associated with a maximum TTI value that isequal to or longer than the TTI associated with resources alreadygranted to the wireless terminal. Thus, the data for the first logicalchannel can be transmitted using the available granted resources. Thedata is encoded (which it is assumed will take one TTI) during theperiod 52, and transmitted in the next-available granted period 54. Uponreceipt by the receiving device (whether that is the radio access nodein the uplink, or another wireless terminal in the sidelink), the datais decoded and this will take a relatively long time owing to the largeramount of data that is transmitted using the longer TTI.

Upon receipt of the control message transmitted in period 52, the radioaccess node decodes the message and provides a new grant of radioresources for the wireless terminal, configured with a TTI value that isequal to or shorter than the maximum TTI value associated with thesecond logical channel. These resources are shown in FIG. 2 as period 56and subsequent periods.

Thus the data associated with the second logical channel is encoded and,in period 56, transmitted to the receiving device using the shorter TTI.As relatively less data is transmitted in the shorter TTI period 56 thanthe longer TTI periods 50, 52, 54, the receiving device requires lesstime to decode the transmission. Thus, even though the data for thesecond logical channel may be transmitted after the data for the firstlogical channel, it is nonetheless received and available earlier in thereceiving device.

FIG. 3 is a flowchart of a method according to embodiments of thedisclosure. The method may be carried out in a wireless terminal, suchas the wireless terminal 16 shown in FIG. 1, for example.

In an optional step 100, the wireless terminal receives, from a radioaccess node, a first grant of first radio resources on which to transmitone or more wireless messages. For example, the radio access node may bea serving radio access node, such as a nodeB, an eNodeB, or similar. Themessage comprising the first grant may be a control message transmittedon a downlink control channel (e.g. PDCCH or sPDCCH) comprising anindication of radio resources which are granted to the wirelessterminal. For example, the control message may comprise downlink controlinformation (DCI) configured in a particular format, e.g. DCI Format 0,to convey an indication of the resources that are granted to thewireless terminal.

The control message may grant resources for the transmission of wirelessmessages in the uplink (i.e. from the wireless terminal to the radioaccess node) or in the sidelink (i.e. from the wireless terminaldirectly to another wireless terminal).

The first radio resources may comprise one or more frequencies (e.g. oneor more frequency sub-channels), one or more time slots, one or moreorthogonal codes used to encode the transmissions, or any combinationthereof. For example, the radio resources may be defined using physicalresource blocks corresponding to particular time slots and frequencies.The resources, and particularly the time slots, may be associated with aparticular TTI value. The TTI value may be explicitly indicated in thecontrol message containing the grant, or implicitly known to thewireless terminal based, for example, on a current mode of operation ofthe wireless terminal, or a format of the control message containing thegrant (i.e. where different formats correspond to different TTI values).

In step 102, the wireless terminal determines that it has data availablefor transmission (i.e. in the uplink or sidelink). For example, thewireless terminal may comprise one or more buffers in which data istemporarily stored prior to being encoded and transmitted. Such data mayarise as a result of some user action (e.g. instigating a call, oraccessing a data service), or an automated process within the wirelessterminal.

The data is associated with one or more logical channels and, in step104, the wireless terminal determines a maximum TTI value associatedwith the logical channels. The logical channels and their associatedparameters (e.g. maximum TTI value, logical channel priority, etc) maybe configured via signalling between the radio access network and thewireless terminal, e.g. using radio resource control (RRC) signalling.

The configuration of parameters may be static or semi-static. Forexample, the parameters for a particular logical channel may persistuntil further notice, or require updating from the radio access network.The parameters may be updated periodically, or on an ad-hoc basis. Thusstep 104 may comprise receiving configuration data for the logicalchannel from the radio access network; however, it is expected that suchconfiguration data will have been received previously and stored locallyin the wireless terminal.

In step 106, the wireless terminal determines whether any granted radioresources are available (i.e. whether any radio resources have beengranted to the wireless terminal, and/or whether such radio resourcesare still available and not allocated for the transmission of otherdata).

If no resources are available the method proceeds to step 108, in whichthe wireless terminal transmits a control message (e.g. a schedulingrequest) to the radio access node requesting the grant of radioresources in which to transmit the data. Thus the control message mayrequest the grant of radio resources associated with a TTI that is equalto or shorter than the maximum TTI value determined in step 104. Forexample, the control message may comprise an explicit or implicitindication of the maximum TTI value (in the latter case, the maximum TTIvalue may be implicitly indicated by a formatting of the controlmessage, for example, or the radio access node may be able to determinethe maximum TTI value by reference to one or more other parameterscontained within the control message).

For example, the control message may be transmitted over an uplinkcontrol channel. The control message may be transmitted using one ormore short transmission opportunities preconfigured in the wirelessterminal (e.g. via signalling with the radio access network) andidentified as an uplink control channel. In one example, the controlmessage is transmitted as a scheduling request over the sPUCCH.

If it is determined in step 106 that resources have been granted to thewireless terminal and are available, the method proceeds to step 110 inwhich the wireless terminal determines whether the maximum TTI valuedetermined in step 104 is less than the TTI value associated with thegranted resources. If the maximum TTI value is not less than the grantedTTI (i.e, it is equal to or greater than the TTI associated with thegranted resources), the granted resources can be used to transmit thedata. Thus, in step 112, the data is encoded and then transmitted usingthe granted resources (e.g. the resources granted in step 100).

Step 108 may comprise allocating the data to the available resources inaccordance with a logical channel priority value associated with thelogical channel for the data. That is, data associated with logicalchannels having a relatively high priority (i.e. having a relativelyhigh logical channel priority value) may be allocated to the availableresources before data associated with logical channels having arelatively low priority (i.e. having a relatively low logical channelpriority value).

If it is determined in step 110 that the maximum TTI value is less thanthe TTI associated with the granted resources, the method proceeds tostep 114, in which the wireless terminal transmits a control message(e.g. a scheduling request) to the radio access node requesting thegrant of radio resources in which to transmit the data. This step may beessentially the same as step 108, for example. Thus the control messagemay request the grant of radio resources associated with a TTI that isequal to or shorter than the maximum TTI value determined in step 104.For example, the control message may comprise an explicit or implicitindication of the maximum TTI value (in the latter case, the maximum TTIvalue may be implicitly indicated by a formatting of the controlmessage, for example, or the radio access node may be able to determinethe maximum TTI value by reference to one or more other parameterscontained within the control message).

For example, the control message may be transmitted over an uplinkcontrol channel. The control message may be transmitted using one ormore short transmission opportunities, and thus, in one example, thecontrol message is transmitted as a scheduling request over the sPUCCH.

In step 118, the wireless terminal receives from the radio access node asecond grant of second radio resources on which to transmit the dataidentified in step 102. The message comprising the second grant may be acontrol message transmitted on a downlink control channel (e.g. PDCCH orsPDCCH) comprising an indication of radio resources which are granted tothe wireless terminal. For example, the control message may comprisedownlink control information (DCI) configured in a particular format,e.g. DCI Format 0, to convey an indication of the resources that aregranted to the wireless terminal.

The control message may grant resources for the transmission of wirelessmessages in the uplink (i.e, from the wireless terminal to the radioaccess node) or in the sidelink (i.e. from the wireless terminaldirectly to another wireless terminal).

The second radio resources may comprise one or more frequencies (e.g.one or more frequency sub-channels), one or more time slots, one or moreorthogonal codes used to encode the transmissions, or any combinationthereof. For example, the radio resources may be defined using physicalresource blocks corresponding to particular time slots and frequencies.The resources, and particularly the time slots, may be associated with aparticular TTI value. The TTI value may be explicitly indicated in thecontrol message containing the grant, or implicitly known to thewireless terminal based, for example, on a current mode of operation ofthe wireless terminal, or a format of the control message containing thegrant (i.e. where different formats correspond to different TTI values).

In accordance with the scheduling request transmitted in step 114, thesecond resources are configured with respect to a TTI value that isshorter than or equal to the maximum TTI value for the logical channelassociated with the data in step 102.

In step 120, the wireless terminal encodes the data and, using thesecond resources identified in the message received in step 118,transmit the data.

As noted above, the conventional response to the detection of dataavailable to transmit is to transmit a buffer status report (BSR)indicating the amount of data that is available to transmit. A BSR maybe transmitted as a control element in the media access control (MAC)layer, and may be transmitted periodically (i.e. indicating a currentamount of data that is available for transmission) or non-periodically(i.e. when data is available for transmission or no data is availablefor transmission).

According to embodiments of the disclosure, the transmission of ascheduling request in step 114 can replace these conventional steps orbe in addition to them. Thus, in one embodiment, after step 114 themethod proceeds to step 116 a in which no BSR is transmitted in respectof the data identified in step 102. For example, the wireless terminalmay be pre-configured to prevent transmission of a BSR in the event thatthe maximum TTI value associated with data available to transmit isshorter than the TTI associated with any granted radio resources, and ascheduling request has been transmitted for further resources configuredwith a shorter TTI. In such embodiments, the network receives a singlerequest for radio resources and respond accordingly.

In an alternative embodiment, after step 114 the method proceeds to step116 b in which a BSR is transmitted in respect of the data identified instep 102. In this case, the radio access node effectively receives tworequests—via different mechanisms—to schedule radio resources for thetransmission of the data identified in step 102. The scheduling requesttransmitted in step 114 may be received and acted upon first by grantingthe second resources described above (especially if transmitted using ashort transmission opportunity). However, the radio access node may takeaccount of the grant of second resources when responding to the BSRtransmitted in step 116 b. If the BSR indicates a relatively smallamount of data, e.g. that could be entirely transmitted using theresources granted in step 118, the radio access node may ignore the BSRtransmitted in step 116 b. If the BSR indicates a greater amount of datathan could be transmitted using the resources granted in step 118, theradio access node may grant further resources for the wireless terminalin which to transmit the remainder of the data.

It will be apparent to those skilled in the art that, although thedescription above has focussed on a process flow for data belonging to asingle logical channel, the method shown in FIG. 3 may be appliedcontinuously for all data that becomes available for transmission. Forexample, data associated with multiple different logical channels maybecome available for transmission simultaneously, or nearlysimultaneously. In that case, separate instances of the method may becarried out in respect of each logical channel in parallel. Thus, ascheduling request message may be transmitted in respect of data for alogical channel associated with a relatively short maximum TTI value(e.g. as shown in step 114), simultaneous with the transmission of datafor a logical channel associated with a relatively long maximum TTIvalue (e.g. as shown in step 112).

It will be apparent from the discussion above that embodiments of thedisclosure provide a method for reducing the latency of urgent wirelesscommunications. This is further apparent from the following examples.

Example 1

Example 1 corresponds to a first example of conventional behaviour, inwhich a wireless terminal transmits a buffer status report following adetermination that data is available for transmission, and issubsequently granted resources having a short TTI. Here we assume that a“long” TTI has 14 OFDM symbols, and is associated with 1 TTI encodingtime and 2 TTI decoding time; while a “short” has 2 OFDM symbols, and isassociated with 2 TTI encoding time and 3 TTI decoding time.

-   -   Wireless terminal determines the presence of data to transmit        and waits for the next long TTI (1-14os)    -   Wireless terminal encodes BSR (assumed zero delay)    -   Wireless terminal sends BSR on the physical uplink shared        channel, PUSCH (14os)    -   Radio access node decodes BSR (2*14os)    -   Radio access node encodes a short UL grant (2*2os)    -   Radio access node transmits short UL grant on sPDCCH (2os)    -   Wireless terminal decodes UL grant and encodes data for        transmission (5*2os)    -   Wireless terminal transmits UL data (2os)    -   Radio access node decodes UL data (3*2os)

This leads to an overall latency of between 67 and 80 OFDM symbols.

Example 2

Example 2 corresponds to a second example of conventional behaviour, inwhich a wireless terminal transmits the data using resources previouslygranted, and configured according to a “long” TTI.

-   -   Wireless terminal determined the presence of data to transmit        and waits for the next long TTI (1-14os)    -   Wireless terminal encodes UL data (1*14os)    -   Wireless terminal transmits UL data (1*14os)    -   Radio access node decodes UL data (2*14os)

This leads to an overall latency of between 57 and 70 OFDM symbols.

Example 3

Example 3 corresponds to the behaviour described above with respect toFIG. 3, in the event that there are no available granted resources, orthe available granted resources are configured with a TTI value that isgreater than the maximum TTI value for the data being transmitted.

-   -   Wireless terminal determines the presence of data to transmit        and waits for the next short TTI (1-4os)    -   Wireless terminal encodes scheduling request (assumed zero        delay)    -   Wireless terminal sends the scheduling request on the sPUCCH        (2os)    -   Radio access node decodes BSR (3*2os)    -   Radio access node encodes a short UL grant (2*2os)    -   Radio access node transmits short UL grant on sPDCCH (2os)    -   Wireless terminal decodes UL grant and encodes data for        transmission (5*2os)    -   Wireless terminal transmits UL data (2os)    -   Radio access node decodes UL data (3*2os)

This leads to an overall latency of between 33 and 36 OFDM symbols.

FIG. 4 is a schematic drawing of a wireless terminal 200 according toembodiments of the disclosure. The wireless terminal 200 may be suitablefor carrying out the method described above, and particularly withrespect to FIG. 3, for example.

The terminal 200 comprises processing circuitry 202 and a non-transitorycomputer-readable medium 204 (such as memory) communicatively coupled tothe processing circuitry 202. The wireless terminal 200 may be operablewithin a wireless communication network, and configurable with aplurality of transmission time intervals.

In one embodiment, the medium 204 stores instructions which, whenexecuted by the processing circuitry 202, cause the terminal 200 to:receive a first grant message from the wireless communication network,the first grant message comprising an indication of first radioresources in which the terminal device can transmit one or more wirelessmessages, the first radio resources being configured according to afirst transmission time interval of the plurality of transmission timeintervals; determine the presence of data to transmit, the data beingassociated with a first logical channel; determine a maximumtransmission time interval associated with the first logical channel;and responsive to a determination that the maximum transmission timeinterval associated with the logical channel is less than the firsttransmission time interval, transmit a scheduling request message to thewireless communication network, the scheduling request message beingconfigured according to a second transmission time interval of theplurality of transmission time intervals, wherein the secondtransmission time interval is shorter than the first transmission timeinterval.

In further embodiments, the terminal 200 may comprise hardware fortransmitting wireless signals (not illustrated), e.g. one or moreantennas, and corresponding transceiver circuitry, coupled to theprocessing circuitry 202 and/or the memory 204.

FIG. 5 is a schematic drawing of a wireless terminal 300 according toembodiments of the disclosure. The wireless terminal 300 may be suitablefor carrying out the method described above, and particularly withrespect to FIG. 3, for example.

The terminal 300 comprises a first module 302, a second module 304, athird module 306 and a fourth module 308. The wireless terminal 300 maybe operable within a wireless communication network, and configurablewith a plurality of transmission time intervals.

In one embodiment, the first module 302 is configured to receive a firstgrant message from the wireless communication network, the first grantmessage comprising an indication of first radio resources in which theterminal device can transmit one or more wireless messages, the firstradio resources being configured according to a first transmission timeinterval of the plurality of transmission time intervals. The secondmodule 304 is configured to determine the presence of data to transmit,the data being associated with a first logical channel. The third module306 is configured to determine a maximum transmission time intervalassociated with the first logical channel. The fourth module 308 isconfigured to, responsive to a determination that the maximumtransmission time interval associated with the logical channel is lessthan the first transmission time interval, transmit a scheduling requestmessage to the wireless communication network, the scheduling requestmessage being configured according to a second transmission timeinterval of the plurality of transmission time intervals, wherein thesecond transmission time interval is shorter than the first transmissiontime interval.

Although the text above has described embodiments of the disclosure inthe context of the 3GPP specifications, specifically Long Term Evolutionand developments thereto, those skilled in the art will appreciate thatthe methods, apparatus and concepts described herein may equally applyto other radio access technologies and the networks that employ them.

The invention claimed is:
 1. A method in a terminal device for awireless communication network, the terminal device being configurablewith a plurality of transmission time intervals, the method comprising:receiving a first grant message from the wireless communication network,the first grant message comprising an indication of first radioresources in which the terminal device can transmit one or more wirelessmessages, the first radio resources being configured according to afirst transmission time interval of the plurality of transmission timeintervals; determining the presence of data to transmit, the data beingassociated with a first logical channel of a plurality of logicalchannels; determining a maximum transmission time interval associatedwith the first logical channel; and responsive to a determination thatthe maximum transmission time interval associated with the first logicalchannel is less than the first transmission time interval, transmittinga scheduling request message to the wireless communication network, thescheduling request message being configured according to a secondtransmission time interval of the plurality of transmission timeintervals, wherein the second transmission time interval is shorter thanthe first transmission time interval.
 2. The method of claim 1, furthercomprising: receiving a second grant message from the wirelesscommunication network, the second grant message comprising an indicationof second radio resources in which the terminal device can transmit oneor more wireless messages, the second radio resources being configuredaccording to a transmission time interval of the plurality oftransmission time intervals that is shorter than the first transmissiontime interval; and transmitting the data using the second radioresources.
 3. The method of claim 2, wherein the transmission timeinterval that is shorter than the first transmission time interval isthe second transmission time interval.
 4. The method of claim 1, furthercomprising: responsive to a determination that the maximum transmissiontime interval associated with the first logical channel is equal to orgreater than the first transmission time interval, transmitting the datausing the first radio resources.
 5. The method of claim 4, wherein thestep of transmitting the data using the first radio resources comprises:determining a priority associated with the first logical channel; andallocating the data to the first radio resources in dependence on thepriority associated with the first logical channel.
 6. The method ofclaim 5, further comprising: allocating data associated with one or moresecond logical channels to the first radio resources in dependence onpriorities associated with the one or more second logical channels. 7.The method of claim 1, wherein the scheduling request message istransmitted via a control channel.
 8. The method of claim 7, wherein thecontrol channel is a short control channel.
 9. The method of claim 7,wherein the control channel is an uplink control channel.
 10. The methodof claim 1, further comprising: responsive to a determination that themaximum transmission time interval associated with the first logicalchannel is less than the first transmission time interval, nottransmitting a buffer status report for the data associated with thefirst logical channel using the first radio resources.
 11. The method ofclaim 1, further comprising: responsive to a determination that themaximum transmission time interval associated with the first logicalchannel is less than the first transmission time interval, transmittinga buffer status report for the data associated with the first logicalchannel using the first radio resources.
 12. The method of claim 1,wherein the first radio resources comprise one or more of: one or moretransmission frequencies, one or more transmission time slots, and oneor more orthogonal codes for encoding.
 13. The method of claim 1,wherein the first radio resources comprise radio resources for thetransmission of one or more uplink messages to the wirelesscommunications network.
 14. The method of claim 1, wherein the firstradio resources comprise radio resources for the transmission of one ormore sidelink messages to another terminal device.
 15. The method ofclaim 1, wherein the association between logical channels and maximumtransmission time intervals is pre configured via radio resource controlsignalling from the wireless communications network.
 16. The method ofclaim 1, wherein the first grant message comprises an indication of thetransmission time interval.
 17. The method of claim 1, wherein the firstlogical channel relates to critical machine-type communications, orultra-reliable low-latency communications.
 18. A terminal device for awireless communication network, the terminal device being configurablewith a plurality of transmission time intervals and comprisingprocessing circuitry and a non-transitory computer-readable mediumstoring instructions which, when executed by the processing circuitry,cause the terminal device to: receive a first grant message from thewireless communication network, the first grant message comprising anindication of first radio resources in which the terminal device cantransmit one or more wireless messages, the first radio resources beingconfigured according to a first transmission time interval of theplurality of transmission time intervals; determine the presence of datato transmit, the data being associated with a first logical channel of aplurality of logical channels; determine a maximum transmission timeinterval associated with the first logical channel; and responsive to adetermination that the maximum transmission time interval associatedwith the first logical channel is less than the first transmission timeinterval, transmit a scheduling request message to the wirelesscommunication network, the scheduling request message being configuredaccording to a second transmission time interval of the plurality oftransmission time intervals, wherein the second transmission timeinterval is shorter than the first transmission time interval.
 19. Theterminal device of claim 18, wherein the non-transitorycomputer-readable medium further stores instructions which, whenexecuted by the processing circuitry, cause the terminal device to:receive a second grant message from the wireless communication network,the second grant message comprising an indication of second radioresources in which the terminal device can transmit one or more wirelessmessages, the second radio resources being configured according to atransmission time interval of the plurality of transmission timeintervals that is shorter than the first transmission time interval; andtransmit the data using the second radio resources.
 20. The terminaldevice of claim 19, wherein the transmission time interval that isshorter than the first transmission time interval is the secondtransmission time interval.
 21. The terminal device of claim 18, whereinthe non-transitory computer-readable medium further stores instructionswhich, when executed by the processing circuitry, cause the terminaldevice to: responsive to a determination that the maximum transmissiontime interval associated with the first logical channel is equal to orgreater than the first transmission time interval, transmit the datausing the first radio resources.
 22. The terminal device of claim 21,wherein the terminal device is caused to transmit the data using thefirst radio resources by: determining a priority associated with thefirst logical channel; and allocating the data to the first radioresources in dependence on the priority associated with the firstlogical channel.
 23. The terminal device of claim 22, wherein thenon-transitory computer-readable medium further stores instructionswhich, when executed by the processing circuitry, cause the terminaldevice to: allocate data associated with one or more second logicalchannels to the first radio resources in dependence on prioritiesassociated with the one or more second logical channels.
 24. Theterminal device of claim 18, wherein the non-transitorycomputer-readable medium further stores instructions which, whenexecuted by the processing circuitry, cause the terminal device to:responsive to a determination that the maximum transmission timeinterval associated with the first logical channel is less than thefirst transmission time interval, not transmit a buffer status reportfor the data associated with the first logical channel using the firstradio resources.
 25. The terminal device of claim 18, wherein thenon-transitory computer-readable medium further stores instructionswhich, when executed by the processing circuitry, cause the terminaldevice to: responsive to a determination that the maximum transmissiontime interval associated with the first logical channel is less than thefirst transmission time interval, transmit a buffer status report forthe data associated with the first logical channel using the first radioresources.
 26. The terminal device of claim 18, wherein the first radioresources comprise radio resources for the transmission of one or moresidelink messages to another terminal device.